Electrosurgical tissue treatment method

ABSTRACT

A medical probe assembly, system, and methods for the use thereof to treat tissue are described. The system optionally comprises an energy source, two internally-cooled probe assemblies, and one or more cooling devices to provide cooling to at least one of the probe assemblies. The probe assemblies may be configured in a bipolar mode, whereby current flows preferentially between the probe assemblies. The probe assemblies and system described herein are particularly useful to deliver radio frequency energy to a patient&#39;s body. RF energy delivery may be used for various applications, including the treatment of pain, tumor ablation and cardiac ablation.

REFERENCES TO PARENT AND CO-PENDING APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.10/087,856, filed Mar. 5, 2002 and claims the benefit of U.S.provisional application No. 60/604,348, filed Aug. 25, 2004.

TECHNICAL FIELD

The present invention relates to a medical device, system and method forapplying energy, particularly radio frequency electrical energy, to apatient's body.

BACKGROUND OF THE ART

The human intervertebral junction is characterized principally by anintervertebral disc interposed between adjacent vertebral surfaces. Thesize and configuration of discs vary between the six discs of thecervical region, the twelve discs of the thoracic region, six of thelumbar region and one disc between the sacrum and coccyx.

Intervertebral discs are neither homogeneous nor static. Changes to adisc can affect the vertebral column activity significantly. Theintervertebral disc is a complex structure where its dynamic propertiesresult from the interaction of a central, gelatinous nucleus pulposusencircled by a tough, fibrous, semielastic annulus fibrosus. Further,thin cartilage endplates and vertebral body ring apophyseal attachmentsof the annulus fibrosus join the disc to the vertebrae craniad andcaudad to the disc. Although the nucleus pulposus is gelatinous andsomewhat fluid while the annulus fibrosus comprises circularly arrangedfibers, the border between these components is not distinct in a healthyadult disc. Any distinction is less apparent in a damaged disc wheretissues are intermingled in a gradual transition layer.

The annulus fibrosus is composed of concentric layers of fibrocartilage,in which collagen fibers are arranged in parallel strands runningobliquely between vertebral bodies. The inclination is reversed inalternate layers thereby crossing over each other obliquely. In childrenand adolescents, the nucleus pulposus is an amorphous colloidal mass ofgelatinous material containing glycosaminoglycans, collagen fibrils,mineral salt, water and cellular elements. The nucleus pulposus has animportant function in nutrition of the disc and contributes to themechanical ability of the disc to act as a shock absorber and allowflexibility. The nucleus pulposus is normally under pressure and iscontained within an ovoid cavity formed laterally by the annulusfibrosus and bounded by thin plates of hyaline cartilage endplatescovering the adjacent vertebrae.

The intervertebral discs form about one-quarter the length of thevertebral column in a healthy adult human. Discs are thickest in thecervical and lumbar regions, where the movements of the vertebral columnare greatest. The vertebral column, including the intervertebral discs,undergo various morphological and biochemical changes over time, such asdehydration of the discs and concaving vertebral bodies. As a result,the size and configuration of the disc components vary considerably fromperson to person.

Lower back injuries and chronic back pain are a major health problemresulting not only in a debilitating condition for the patient, but alsoin the consumption of a large proportion of funds allocated for healthcare, social assistance and disability programs. Disc abnormalities andpain may result from trauma, repetitive use in the workplace, metabolicdisorders, inherited proclivity or aging. The existence of adjacentnerve structures and innervation of the disc are very important issuesin respect to patient treatment for back pain.

Common disorders of the intervertebral disc include localized tears orfissures in the annulus fibrosus; disc herniations with contained orescaped extrusions of the nucleus pulposus; and chronic circumferentialbulging of discs. For most patients, however, a well-defined abnormalitycannot be found to solely explain the cause of the low back pain, makingtreatment and pain management very difficult. Since isolating a specificanatomic disorder as the sole cause of pain is rare, most patients aremerely treated symptomatically to reduce pain, rather than receivingtreatment to eliminate the cause of the condition.

One course of pain may be attributed to the structure of the annulusfibrosus. The annulus fibrosus is thinner nearer to the posterior thanto the anterior margin of the disc, and many disc ruptures occur in theposterior region thereby exerting pressure on the adjacent nerve fiberscausing pain. The pain experienced by the disc exerting pressure on theadjacent nerves is characterized by referred pain, or pain feltpredominantly elsewhere in the body where the affected nerve travels. Acommon example of this is sciatica where an intervertebral disc exertspressure on the sciatic nerve.

Another cause of pain resulting from disc pathology ischemically-induced pain. The nucleus pulposus contains chemicals thatmay induce pain if contact is made with certain nerve structures. If anintervertebral disc is herniated severely enough that a portion of thenucleus pulposus is extruded from the disc, and the portion comes incontact with an adjacent nerve, chemically-induced pain can be felt.This is also a cause of sciatica.

Increasingly, evidence suggests that the source of back pain in manypatients is a result of nerves within the degenerated disc itself ornerves that have grown into the disc in concordance with disc injury.For example, as documented by Jonathan C. Houpt, B A, Edison S. Conner,M D, and Eric W. McFarland in “Experimental Study of TemperatureDistributions and Thermal Transport During Radio frequency CurrentTherapy of the Intervertebral Disc”, Spine. 1996; 21(15), 1808-1813,afferent innervation of the outer half of the annulus fibrosus has beenestablished whereas the nucleus pulposus contains no nerves or bloodvessels. Pain response has been widely reported in response to specificstimulation of the outer layers of the annulus fibrosus. In anotherstudy documented by A. J. Freemont, “Nerve ingrowth into diseasedintervertebral disc in chronic back pain”, The Lancet. 1997; 350,178-181, nociceptive nerves were found ingrown deeper into the disc, asfar as the nucleus pulposus, in association with disc degeneration. Thepain experienced from nerves in a damaged intervertebral disc is morelocalized to the spine. The stimulation can be both mechanical andchemical. Some patients may feel a combination of back pain and referredpain indicating that pain is being transmitted both from nerves in thedisc and from impinged nerves adjacent to the disc. It appears that thedisc is devoid of temperature-sensing neurological structures, possiblydue to the fact that the disc is at core body temperature, and onlymechanical and chemical stimulus-sensing nociceptors exist in the disc.

Where patients are diagnosed with clear chronic discogenic pain (i.e.pain originating from a disc), complete surgical removal of theintervertebral disc (called discectomy) and fusion of the adjacentvertebrae is often carried out with success rates over 80% in measurablepain reduction after surgery. Such major surgical procedures are highlyinvasive, expensive and involve significant risk. Furthermore motion isimpeded once the vertebrae are fused and there may be adverse mechanicaleffects on the adjacent remaining discs.

To alleviate some of the disadvantages of open-surgery discectomy,percutaneous methods of removing the disc or part of the disc have beenpracticed. Methods that remove part of the nucleus pulposus are designedto decrease the volume in order to reduce internal disc pressure thusreducing external pressure exerted on adjacent nerves. Examples of suchmethods that include mechanical means can be found in, for example, U.S.Pat. No. 4,369,788 to Goald that describes the use of a mechanicaldevice for use in microlumbar discectomy, and in U.S. Pat. No. 5,201,729to Hertzmann et al. that describes a percutaneous method of discectomyusing a laser. Other methods of removing the disc or part of the discinclude chemically dissolving the nucleus pulposus using the enzymeChymopapain. U.S. Pat. No. 6,264,650 to Hovda et al. describes a methodof vaporizing a portion of the nucleus pulposus using radio frequencyelectrical current. These prior art methods have shown variable successand there are several advantages of percutaneous procedures over opensurgical discectomy and vertebral fusion including less trauma to thepatient, preserved spinal movement, less disruptive effect on adjacentdiscs, less risk of infection and less risk of accidental injury.However, these methods involve removing a portion of the nucleuspulposus, which is essential to the maintenance of the disc. Further,the damaged annulus fibrosus is not treated.

Due to the pain reduction success of surgical discectomy, less drasticmeans of denervating rather than surgically removing the disc are ofsignificant interest. To denervate is to intervene with the transmissionof a sensory signal in a nerve. A denervated disc does not causediscogenic pain and the disc is left intact to preserve its mechanicalfunction. Denervating the disc especially by using percutaneous probesis much less invasive, less costly and less risky. The procedure is alsosimpler to administer and does not require the fusing of adjacentvertebrae thereby better preserving the patient's freedom of movement.

A minimally invasive technique of delivering high-frequency electricalcurrent has been shown to relieve localized pain in many patients.Generally, the high-frequency current used for such procedures is in theradio frequency (RF) range, i.e. between 100 kHz and 1 GHz and morespecifically between 300-600 kHz. The RF electrical current is typicallydelivered from a generator via connected electrodes that are placed in apatient's body, in a region of tissue that contains a neural structuresuspected of transmitting pain signals to the brain. The electrodesgenerally include an insulated shaft with an exposed conductive tip todeliver the radio frequency electrical current. Tissue resistance to thecurrent causes heating of tissue adjacent resulting in the coagulationof cells (at a temperature of approximately 45° C. for smallunmyelinated nerve structures) and the formation of a lesion thateffectively denervates the neural structure in question. Denervationrefers to a procedure whereby the ability of a neural structure totransmit signals is affected in some way and usually results in thecomplete inability of a neural structure to transmit signals, thusremoving the pain sensations. This procedure may be done in a monopolarmode where a second dispersive electrode with a large surface area isplaced on the surface of a patient's body to complete the circuit, or ina bipolar mode where a second radio frequency electrode is placed at thetreatment site. In a bipolar procedure, the current is preferentiallyconcentrated between the two electrodes.

In order to extend the size of a lesion, radio frequency treatment maybe applied in conjunction with a cooling mechanism, whereby a coolingmeans is used to reduce the temperature of the tissue in the vicinity ofan energy delivery device, allowing a higher voltage to be appliedwithout causing an unwanted increase in local tissue temperature. Theapplication of a higher voltage allows regions of tissue further awayfrom the energy delivery device to reach a temperature at which a lesioncan form, thus increasing the size/volume of the lesion

The treatment of pain using high-frequency electrical current has beenapplied successfully to various regions of patients' bodies suspected ofcontributing to chronic pain sensations. For example, with respect toback pain, which affects millions of individuals every year,high-frequency electrical treatment has been applied to several tissues,including intervertebral discs, facet joints, sacroiliac joints as wellas the vertebrae themselves (in a process known as intraosseousdenervation). In addition to creating lesions in neural structures,application of RF energy has also been used to treat tumors throughoutthe body.

In an effort to reduce back pain through early intervention techniques,some investigators have focused upon nerves contained within thevertebral bodies which are adjacent to the intervertebral discs. Forexample, in PCT Patent Publication No. WO 01/0157655, Heggenessdiscloses ablating nerves contained within the vertebral body(intraosseous nerves) by first boring into the vertebral body with anerve ablation device, placing the tip of the device in close proximityto the nerve, and then ablating the nerve using the tip. However,previous techniques fail to describe how to effectively carry out nerveablation when the precise location of the intraosseous nerve is unknown,or when the electrode tip cannot be maneuvered relatively close to theintraosseous nerve.

With respect to the intervertebral disc itself, U.S. Pat. No. 5,433,739to Sluijter et al. describes a method of relieving back pain throughpercutaneous insertion of a needle or electrode into the center of theintervertebral disc within the nucleus pulposus under fluoroscopy orother imaging control. The U.S. Pat. No. 5,433,739 patent describes theheating of the outer layers of the annulus fibrosus to a temperaturethat is lethal to the nerve structures thereby denervating the disc torelieve discogenic pain. The temperature of the tissue is increased byapplying high frequency electric current through the tissue.

It is well known to those skilled in the art that percutaneous access toan intervertebral lumbar disc involves either a posterolateral approachor an anterior approach. The anterior approach is more invasive than theposterolateral approach because of the organs in the abdominal andpelvic cavities. The most common percutaneous approach to the lumbardisc, to those skilled in the art, is to insert a needle or tubeposterolateral to the disc, just lateral of the zygapophyseal joint,inferior to the spinal nerve and into the posterolateral region of theannulus fibrosus.

In accordance with U.S. Pat. Nos. 5,980,504; 6,007,570; 6,073,051;6,095,149; 6,099,514; 6,122,549; 6,126,682; 6,258,086 B1; 6,261,311 B1;6,283,960 B1; and 6,290,715 B1 (“the Sharkey et al. patents”) to Sharkeyet al. to permit percutaneous access to the posterior half of thenucleus or to the posterior inner wall of the disc, a flexible heatingelement may be inserted into the nucleus pulposus through a hollow tubethat has been inserted through the annulus fibrosus. The flexibleheating element has sufficient rigidity to be advanced longitudinallyunder force through the nucleus pulposus while having sufficientflexibility to be compliant to the inner wall of the annulus fibrosus.The heating element is guided by sliding contact with the inner wall andideally should not puncture or damage the annulus fibrosus duringpositioning. Another embodiment disclosed in U.S. Pat. No. 6,258,086 B1is a flexible probe that contains an activation element on the distalportion that changes the shape of the probe once it is in the nucleuspulposus. According to the Sharkey et al. patents, the flexible heatingelements operate to denervate the outer layers of the annulus fibrosusas well as modulate the collagen in the annulus fibrosus by applyingheat. Raising the temperature above about 60° C. will break structuralbonds of collagen fibers causing them to contract and tighten. Thiscollagen-tightening effect is lost once the temperature of the collagenis raised above about 75° C. where the fibers loosen, resulting in zeronet volume change.

There is interest among researchers that the application of highfrequency current without a rise in temperature alters nerve function torelieve pain. Use of high frequency current without heating to relievepain by modifying neural tissue is described in U.S. Pat. Nos.5,983,141; 6,161,048; 6,246,912; and 6,259,952 (“the Sluijter et al.patents”) to Sluijter et al. These patents describe the use of amodified signal wave that includes rest periods to allow heat todissipate. The modified high frequency signal is applied to the patientusing a single active electrode and a ground electrode attached to theskin of the patient. These disclosures (the Sluijter et al. patents) donot discuss using high frequency current to increase collagen productionnor do they discuss this application in the intervertebral disc. Thedisclosures that are specifically designed for treatment ofintervertebral discs (the Sharkey et al. patents; U.S. Pat. No.5,433,739 of Sluijter et al.; and Finch PCT publication number WO01/45579) do not discuss the application of high frequency currentwithout a rise in temperature to alter nerve function to relieve pain orto cause collagen production to increase. The advantages of non-thermalapplication of high frequency electrical current to treat intervertebraldiscs include reduced risk of thermal damage, increased production ofcollagen to strengthen the annulus fibrosus, and reduced discogenic painwhile stimulating the healing processes.

The above referenced publications describe the use of monopolar devicesfor treatment procedures and are therefore restricted by the limitationsof using a monopolar probe. For example, since energy is primarilyconcentrated around the lone electrode in a monopolar device, preciseknowledge of the location of the tissue to be treated is required. Incontrast, in a bipolar procedure, the energy is concentrated between twoelectrodes allowing a tissue to be affected by the treatment procedureprovided it is located substantially between the electrodes. The use oftwo electrodes in a bipolar configuration also allows for the creationof a more uniform lesion than with a single electrode where the energyis concentrated at the surface of the electrode.

Thus, it would be beneficial to have a device and a system thatovercomes some or all of the limitations of the prior art.

SUMMARY OF THE INVENTION

There is a continued need for improvement in systems used for RFtreatment of bodily tissue. Specifically, it would be beneficial toincorporate cooled probes and temperature and impedance monitoringconcepts into an RF treatment system. In addition, the system should becapable of providing newer treatment modalities, such as bipolar RF.Finally, the probes used in the system should be relatively compactwhile still providing the benefits and advantages mentioned herein.Thus, the present invention attempts to overcome some or all of thedeficiencies in the prior art.

In accordance with a first aspect of the present invention, a method oftreating spinal tissue of a patient's body is provided. The methodoptionally comprises the following steps: (i) providing an energy sourceand first and second internally-cooled probe assemblies, wherein each ofthe probe assemblies comprises an electrically conductive energydelivery device electrically coupled to said energy source; (ii)inserting the energy delivery devices of the first and secondinternally-cooled probe assemblies into spaced-apart treatment sites forthe spinal tissue; and (iii) delivering energy from the energy source tothe spinal tissue through said energy delivery devices.

As a feature of this aspect of the present invention, the step ofinserting the energy delivery devices may further comprise inserting atleast one introducer tube into a patient's body, wherein the energydelivery devices may be inserted into the treatment sites through a boreof the at least one introducer tube. Additionally, the step of insertingthe energy delivery devices may further comprise utilizing an aid, forexample fluoroscopic imaging, impedance monitoring or tactile feedback,to assist in positioning at least one of the energy delivery devices. Asa further feature of this method aspect, the method may further comprisethe steps of: (i) providing an apparatus operable to deliver a coolingmeans to at least one probe assembly inserted into a treatment site; and(ii) delivering the cooling means to at least one of the first andsecond internally-cooled probe assemblies when the energy deliverydevices are located at the spaced-apart treatment sites.

In accordance with an additional feature of the method of the presentinvention, the method may comprise a further step of deliveringstimulating energy through at least one of said energy delivery devicesfor determining proximity of at least one of the energy delivery devicesto a neural structure. The stimulating energy may be capable ofeliciting a response from the neural structure without damaging theneural structure. Furthermore, the step of delivering stimulating energymay comprise delivering the stimulating preferentially between theenergy delivery devices in a bipolar manner.

As an additional feature of this aspect of the present invention, themethod may further comprise a step of at least one of inserting materialto and removing material from the spinal tissue, wherein the step of atleast one of inserting and removing material may be performed at leastone of before and after the delivery of energy. For example, a treatmentcomposition such as an anesthetic, a dye or an antibiotic may beinjected into the spinal tissue.

As yet a further feature of this aspect of the present invention, themethod may further comprise the steps of: (i) providing at least oneadditional electrically conductive component electrically coupled to theenergy source and operable to transmit energy between the energy sourceand the patient's body; and (ii) controlling a flow of energy between atleast two electrically conductive components selected from the groupconsisting of the first probe assembly, the second probe assembly andthe at least one additional electrically conductive component; whereinthe step of controlling a flow of energy may comprise altering anelectrical impedance between a current sink and at least oneelectrically conductive component selected from the group consisting ofthe first probe assembly, the second probe assembly and the at least oneadditional electrically conductive component.

The spinal tissue being treated may be selected from the groupconsisting of an intervertebral disc, spinal neural tissue and avertebra or portions thereof. Furthermore, the energy source may be aradio-frequency generator and the step of delivering energy may comprisedelivering electrical current in a radio-frequency range. Additionally,the energy delivery devices may be operated in a bipolar mode, wherebydelivered energy is preferentially concentrated between the energydelivery devices.

As a further feature of this method aspect, the system may furthercomprise a controller operable to control at least one aspect of atreatment protocol selected from the group consisting of energy deliveryand cooling supply. Furthermore, the controller may be operable tocontrol the at least one aspect based on at least one of a temperaturemeasurement, an impedance measurement and an error signal. In addition,the method may further comprise a step of measuring a treatmentparameter, for example temperature or impedance, and altering the atleast one aspect of a treatment protocol based on a measured treatmentparameter.

As a feature of this aspect of the present invention, theinternally-cooled probe assemblies may comprise an elongate memberhaving a distal region and a proximal region and defining a lumentherebetween, an energy delivery device, comprising a protrusion,associated with the distal region of the elongate member and atemperature sensor associated with the protrusion. The internally-cooledprobe assemblies may each further comprise at least two tubular membersdisposed within the lumen for delivering a cooling fluid to an removinga cooling fluid from the energy delivery devices.

In accordance with a second aspect of the present invention, a medicalprobe assembly for delivering energy to a patient's body is provided.The probe assembly optionally comprises an elongate member having adistal region and a proximal region and defining a lumen therebetween,an energy delivery device, comprising a protrusion, associated with thedistal region of the elongate member and a temperature sensor associatedwith the protrusion of the energy delivery device. The temperaturesensor may, for example, be selected from the group consisting of athermocouple, a thermistor, a thermometer and an optical fluorescentsensor. In addition, if the temperature sensor is a thermocouple, theprotrusion may be a component of the thermocouple.

As a feature of this aspect of the present invention, the probe assemblymay further comprise at least two tubular members disposed within thelumen for delivering a fluid to and removing a fluid from the energydelivery device. For example, the tubular members may be hypotubes andthe fluid delivered to the energy delivery device may serve to reducethe temperature of tissue surrounding the energy delivery device. Thetubular members may be located adjacent to each other and they may becoupled to another two flexible tubular members associated with theproximal region of the elongate member.

As additional features of this aspect of the present invention, theprobe assembly may further comprise at least one secondary temperaturesensor. This temperature sensor may also be selected from the groupconsisting of a thermocouple, a thermistor, a thermometer and an opticalfluorescent sensor and may be located at any location of the probeassembly. For example, the secondary temperature sensor may be locatedat the distal region of the elongate member, proximal from thetemperature sensor associated with the protrusion of the energy deliverydevice. The secondary temperature sensor may also be located on anoptional introducer tube or on a separate elongate member inserted intoa patient's body. The probe assembly may also comprise at least onemarker selected from the group consisting of a radiopaque marker, avisible marker and a tactile marker. In addition, the probe assembly maycomprise an active shape control mechanism for directing at least aportion of the distal region of the elongate member as it is advancedthrough said patient's body.

In accordance with a second method aspect of the present invention, amethod of treating spinal tissue of a patient's body by deliveringenergy from an energy source to the patient's body is provided. Themethod optionally comprises the following steps: (i) providing first andsecond internally-cooled probe assemblies and at least one additionalelectrically conductive component, wherein each of the probe assembliescomprises an electrically conductive energy delivery device electricallycoupled to the energy source; (ii) delivering energy from the energysource to spaced-apart treatment sites for the spinal tissue throughsaid energy delivery devices; and (iv) altering an electrical impedancebetween a current sink and at least one electrically conductivecomponent selected from the group consisting of the first probeassembly, the second probe assembly and the at least one additionalelectrically conductive component; whereby altering an electricalimpedance serves to adjust a flow of energy between at least twoelectrically conductive components selected from the group consisting ofthe first probe assembly, the second probe assembly and the at least oneadditional electrically conductive component.

In accordance with a third aspect of the present invention, a system fordelivering energy to a patient's body is provided. The system optionallycomprises (i) an energy source (ii) at least two probe assemblies (iii)an apparatus coupled to at least two of the probe assemblies, saidapparatus operable to reduce a temperature of the probe assemblies towhich it is coupled and (iv) a controller operable to control anoperation of the apparatus with respect to each of the probe assembliesto which it is coupled, whereby the operation of the apparatus for oneprobe is independent of the operation of the apparatus for anotherprobe.

As a feature of this aspect of the present invention, the energy sourcemay comprise an electrical generator, wherein the generator may beoperable to provide energy selected from the group consisting ofradio-frequency (RF) energy and microwave energy. As an additionalfeature, the apparatus may comprise at least one peristaltic pump fordelivering a cooling fluid to the probe assemblies to which it'scoupled. Furthermore, the at least two probe assemblies may eachcomprise an elongate member having a distal region and a proximal regionand defining a lumen therebetween, an energy delivery device, comprisinga protrusion, associated with said distal region of said elongate memberand a temperature sensor associated with said protrusion. In addition,each of the probe assemblies to which the apparatus is coupled mayfurther comprise at least two tubular members disposed within the lumenfor delivering a fluid to and removing a fluid from the energy deliverydevice.

In accordance with a fourth aspect of the present invention, a systemfor delivering energy to a patient's body is provided. The systemoptionally comprises (i) an energy source (ii) at least two probeassemblies (iii) a cooling means coupled to at least two of the probeassemblies, the cooling means operable to reduce a temperature of theprobe assemblies to which it is coupled and (iv) a means for controllingan operation of the cooling means with respect to each of the probeassemblies to which it is coupled, whereby the operation of said coolingmeans for one probe is independent of the operation of said coolingmeans for another probe.

These features and others will become apparent in the detaileddescription that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be readily understood, embodiments ofthe invention are illustrated by way of examples in the accompanyingdrawings, in which:

FIG. 1 is an illustration of a portion of a first embodiment of a systemof the present invention;

FIGS. 2A to 2F depict side views of alternate embodiments of a distaltip region of a probe assembly;

FIG. 3A is an isometric view of one embodiment of the handle of theprobe assembly of the present invention.

FIG. 3B is a longitudinal cross-section of one embodiment of a handle ofthe probe assembly of the present invention;

FIG. 4 is a perspective cut-away view of one embodiment of a distal tipregion of a probe assembly of the present invention;

FIG. 5A is an axial cross-section through the distal tip region of theprobe assembly shown in FIG. 4;

FIG. 5B is an axial cross-section through a more proximal portion of thedistal tip region of the probe assembly shown in FIG. 4;

FIGS. 6A-6C are sectional views of various embodiments of aliquid-cooled distal tip region of a probe assembly;

FIG. 7 is a sectional view of an embodiment of a liquid-cooled distaltip region comprising an impedance monitoring tip;

FIG. 8 shows two probes placed within an intervertebral disc;

FIGS. 9A and 9B are sectional views of alternate embodiments of aliquid-cooled distal tip region illustrating various embodiments of atemperature sensing element;

FIG. 10 is a lateral view of a portion of a human spine;

FIGS. 11A and 11B show possible placements of two probe assemblies in anintervertebral disc;

FIG. 12A is a graph of temperature in a uniform tissue vs. relativedistance using cooled and non-cooled probe assemblies; and

FIG. 12B is a graph of energy in a uniform tissue vs. relative distanceusing cooled and non-cooled probe assemblies.

DETAILED DESCRIPTION OF THE INVENTION

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of some embodiments of the present inventiononly, and are presented in the cause of providing what is believed to bethe most useful and readily understood description of the principles andconceptual aspects of the invention. In this regard, no attempt is madeto show structural details of the invention in more detail than isnecessary for a fundamental understanding of the invention, thedescription taken with the drawings making apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

For the purposes of this invention, a lesion refers to any effectachieved through the application of energy to a tissue in a patient'sbody, and the invention is not intended to be limited in this regard.Furthermore, for the purposes of this description, proximal generallyindicates that portion of a device or system next to or nearer to a user(when the device is in use), while the term distal generally indicates aportion further away from the user (when the device is in use).

With reference to FIG. 1, a first embodiment of a system 100 of thepresent invention is shown. System 100 comprises a generator 102, acable 104, first and second probe assemblies 106 (only one probeassembly is shown), one or more cooling devices 108, a pump cable 110,one or more proximal cooling supply tubes 112 and one or more proximalcooling return tubes 114. In this embodiment, generator 102 is a radiofrequency (RF) generator, but may optionally be any energy source thatmay deliver other forms of energy, including but not limited tomicrowave energy, thermal energy, ultrasound and optical energy.Generator 102 may comprise a display means incorporated into saidgenerator. Said display means may be operable to display various aspectsof a treatment procedure, including but not limited to any parametersthat are relevant to a treatment procedure, such as temperature,impedance, etc. and errors or warnings related to a treatment procedure.If no display means is incorporated into generator 102, generator 102may comprise a means of transmitting a signal to an external display. Inthe first embodiment, generator 102 is operable to communicate with onemore devices, for example with one or more of first and second probeassemblies 106 and the one or more cooling devices 108. Suchcommunication may be unidirectional or bidirectional depending on thedevices used and the procedure performed. An example of an RF generatorthat fulfills the above criteria is the Pain Management Generator (PMG)of Baylis Medical Company Inc. (Montreal, QC, Canada).

As illustrated in FIG. 1, in this first embodiment of a system of thepresent invention, a distal region 124 of cable 104 comprises a splitter130 that divides cable 104 into two distal ends 136 as illustrated inFIG. 1 such that two probe assemblies 106 can be connected to cable 104.A proximal end 128 of cable 104 is connected to generator 102. Thisconnection can be permanent, whereby, for example, the proximal end 128of cable 104 is embedded within generator 102, or temporary, whereby,for example, the proximal end 128 of cable 104 is connected to generator102 via an electrical connector. The two distal ends 136 of cable 104terminate in connectors 140 operable to couple to probe assemblies 106and establish an electrical connection between probe assemblies 106 andgenerator 102. In alternate embodiments (not shown), system 100 maycomprise a separate cable for each probe assembly 106 being used tocouple probe assemblies 106 to generator 102. Alternatively, splitter130 may comprise more than two distal ends. Such a connector would beuseful in embodiments where it would be desirable to connect more thantwo devices to generator 102, for example, if more than two probeassemblies are being used or if separate temperature sensors (i.e. notattached to the probe assemblies) are to be placed in a patient's body.

One or more cooling devices 108 may comprise any means of reducing atemperature of material located at and proximate to one or more of probeassemblies 106. In the first embodiment, one or more cooling devices 108comprises two peristaltic pumps operable to circulate a fluid from theone or more cooling devices 108 through one or more proximal coolingsupply tubes 112, probe assemblies 106, one or more proximal coolingreturn tubes 114 and back to the one or more cooling devices 108. Thefluid may be water or any other suitable fluid. In alternateembodiments, one or more cooling devices 108 may comprise only oneperistaltic pump or one or more electrothermal cooling devices or anyother cooling means.

In the first embodiment, system 100 comprises a means of facilitatingcommunication between the one or more cooling devices 108 and generator102, and one or more cooling devices 108 is operable to communicate atleast uni-directionally and optionally bi-directionally, with generator102. In this way, feedback control is established between the one ormore cooling devices 108 and the generator 102. The feedback control ofthe first embodiment of the present invention involves generator 102,first and second probe assemblies 106 and the one or more coolingdevices 108, although any feedback between any two devices is within thescope of the present invention. The feedback control may be implemented,for example, in a controller or control module which may be a componentof generator 102. In this embodiment, generator 102 is operable tocommunicate bi-directionally with first and second probe assemblies 106as well as with the one or more cooling devices 108. In the context ofthis invention, bi-directional communication refers to the capability ofa device to both receive a signal from and send a signal to anotherdevice.

As an example of feedback control in system 100 of the presentinvention, generator 102 may receive temperature measurements from oneor both of first and second probe assemblies 106. Based on thetemperature measurements, generator 102 may perform some action, such asmodulating the power that is sent to first and/or second probeassemblies 106. Thus, both probe assemblies 106 may be individuallycontrolled based on their respective temperature measurements. Forexample, power to each of the probe assemblies could be increased when atemperature measurement is low or decreased when a measurement is high.This variation of power may be different for each probe assembly. Insome cases, generator 102 may terminate power to one or more probeassemblies 106. Thus, generator 102 may receive a signal (e.g.temperature measurement) from one or both of first and second probeassemblies 106, determine the appropriate action, and send a signal(e.g. decreased or increased power) back to one or both of first andsecond probe assemblies 106. Alternatively, generator 102 may send asignal to the one or more cooling devices 108 to either increase ordecrease the flow rate or degree of cooling being supplied to one orboth of first and second probe assemblies 106.

Alternatively, if one or more cooling devices 108 comprises one or moreperistaltic pumps, the one or more pumps may communicate a fluid flowrate to generator 102 and may receive communications from generator 102instructing the pumps to modulate this flow rate. In some instances, theone or more peristaltic pumps may respond to generator 102 by changingthe flow rate or turning off for a period of time. With cooling devices108 turned off, any temperature sensing elements associated with probeassemblies 106 would not be affected by the cooling fluid allowing amore precise determination of the surrounding tissue temperature to bemade. In addition, when using more than one probe assembly 106, theaverage temperature or a maximum temperature in the temperature sensingelements associated with probe assemblies 106 may be used to modulatecooling.

In other embodiments, the one or more cooling devices 108 may reduce therate of cooling or disengage depending on the distance between the probeassemblies 106. For example, when the distance is small enough such thata sufficient current density exists in the region to achieve a desiredtemperature, little or no cooling may be required. In such anembodiment, energy is preferentially concentrated between first andsecond energy delivery devices 192 through a region of tissue to betreated, thereby creating a strip lesion. A strip lesion ischaracterized by an oblong volume of heated tissue that is formed whenan active electrode is in close proximity to a return electrode ofsimilar dimensions. This occurs because at a given power, the currentdensity is preferentially concentrated between the electrodes and a risein temperature results from current density.

One or more cooling devices 108 may also communicate with generator 102in order to alert generator 102 to one or more possible errors and/oranomalies associated with one or more cooling devices 108. For example,if cooling flow is impeded or if a lid of the one or more coolingdevices 108 is opened. Generator 102 may then act on the error signal byat least one of alerting a user, aborting the procedure, and modifyingan action.

In still other embodiments, generator 102 may communicate with only oneof the one or more cooling devices 108 or communication between devicesmay be uni-directional. For example, the one or more cooling devices 108may be operable to receive incoming signals from generator 102 but notto send signals back to generator 102. In addition to the aforementionedfeedback systems, generator 102 may respond to Somatosensory evokedpotentials (SSEP)/Electromyogram (EMG) measurements or some othermeasure of patient response to a treatment procedure. Many variations infeedback control may exist in a system of the present invention, and theinvention is not limited in this regard.

As illustrated in FIG. 1, the means of facilitating communicationbetween the one or more cooling devices 108 and generator 102 may takethe form of a pump cable 110 electrically connecting generator 102 tothe one or more cooling devices 108. In other embodiments, generator 102and the one or more cooling devices 108 may be connected with an RS-232cable, a fiber optic cable, a USB cable, a Firewire™ (ieee 1394) cableor other means of electrical coupling. In yet further embodiments,communication between generator 102 and the one or more cooling devices108 may be achieved using some other communication protocol includingbut not limited to infrared, wireless, Bluetooth™ and others and theinvention is not limited in this regard.

In the first embodiment of a system of the invention as illustrated inFIG. 1, the one or more proximal cooling supply tubes 112 compriseproximal supply tube connectors 116 at the distal ends of the one ormore proximal cooling supply tubes 112. Additionally, the one or moreproximal cooling return tubes 114 comprise proximal return tubeconnectors 118 at the distal ends of the one or more proximal coolingreturn tubes 114. In the first embodiment, proximal supply tubeconnectors 116 are female luer-lock type connectors and proximal returntube connectors 118 are male luer-lock type connectors although otherconnector types are intended to be within the scope of the presentinvention.

In the first embodiment of a system of the present invention andreferring still to FIG. 1, probe assembly 106 comprises a proximalregion 160, a handle 180, a hollow elongate shaft 184 and a distal tipregion 190 comprising one or more energy delivery devices 192. Proximalregion 160 comprises distal cooling supply tube 162, distal supply tubeconnector 166, distal cooling return tube 164, distal return tubeconnector 168, probe assembly cable 170 and probe cable connector 172.In this embodiment, distal cooling supply tube 162 and distal coolingreturn tube 164 are flexible to allow for greater maneuverability ofprobe assemblies 106, but alternate embodiments with rigid tubes arepossible.

In a first embodiment, distal supply tube connector 166 is a maleluer-lock type connector and distal return tube connector 168 is afemale luer-lock type connector. Thus, proximal supply tube connector116 is operable to interlock with distal supply tube connector 166 andproximal return tube connector 118 is operable to interlock with distalreturn tube connector 168. This helps to establish a circuit withinwhich a cooling fluid may flow while maintaining modularity of probeassembly 106. As a further benefit, having different types of connectorson either proximal tube as well as different types of connectors oneither distal tube adds a measure of safety by ensuring that the tubeswill not be connected incorrectly (i.e. supply to return and viceversa).

In the first embodiment illustrated in FIG. 1, probe cable connector 172is located at a proximal end of probe assembly cable 170 and is operableto reversibly couple to one of connectors 140, thus establishing anelectrical connection between generator 102 and probe assembly 106.Probe assembly cable 170 comprises one or more conductors depending onthe specific configuration of probe assembly 106. For example, in thisembodiment of system 100 of the present invention, probe assembly cable170 comprises five conductors allowing probe assembly cable 170 totransmit RF current from generator 102 to the one or more energydelivery devices 192 as well as to connect multiple temperature sensingdevices to generator 102 as discussed below.

One or more energy delivery devices 192 may comprise any means ofdelivering energy to a region of tissue adjacent distal tip region 190.For example, the one or more energy delivery devices 192 may comprise anultrasonic device, an electrode or any other energy delivery means andthe invention is not limited in this regard. Similarly, energy deliveredvia the one or more energy delivery devices 192 may take several formsincluding but not limited to thermal energy, ultrasonic energy, radiofrequency energy, microwave energy or any other form of energy. In afirst embodiment, the one or more energy delivery devices 192 comprisean electrode. The active region of the electrode may be 2-20 mm inlength and energy delivered by the electrode is electrical energy in theform of current in the RF range. The size of the active region of theelectrode in this embodiment is optimized for placement within anintervertebral disc, however, different sizes of active regions, all ofwhich are within the scope of the present invention, may be useddepending on the specific procedure being performed. In someembodiments, feedback from generator 102 may automatically adjust theexposed area of energy delivery device 192 in response to a givenmeasurement such as impedance or temperature. This may be accomplishedthrough the use of an adjustable insulation sleeve associated withenergy delivery device 192. Adjustment of the insulation sleeve could beaccomplished through sliding the sleeve proximally or distally along theenergy delivery device. The adjustment may be done manually in otherembodiments. Alternatively, additional conductive regions may beprovided along distal tip region 190 proximate energy delivery device192. In such an embodiment, the size or shape of a lesion may be alteredby selectively delivering energy through one or more of the additionalconductive regions and energy delivery device 192. Furthermore, one ormore energy delivery devices 192 may comprise any combination of activeelectrodes and return electrodes, as is well known in the art.

FIGS. 2A-2F show different shapes which the distal end of energydelivery device 192 can adopt for insertion in the patient's body. FIG.2A shows a pencil tip. FIG. 2B shows a sharp beveled tip. FIG. 2C showsa blunt end when cutting or piercing is not required. FIGS. 2D and 2Eshow front and side views of a spatula shaped tip whereas FIG. 2F showsa curved tip with a cutting bevel end. The different shapes can allowfor the current to be directed into the disc in a profile correspondingto the shape of the tip, thereby controlling the current density whichwill in turn control the size and shape of a lesion created in thetissue. These embodiments are intended to be exemplary only and varioustip shapes may be used with the invention.

Cooling can be supplied to the one or more energy delivery devices 192in various ways. The scope of the present invention includes any and allcooling means known in the art that may be used to provide cooling tothe one or more energy delivery devices 192 and is not limited in thisregard. In a first embodiment as has been described earlier, and withreference now to FIG. 3, distal cooling supply tube 162 and distalcooling return tube 164 are connected to shaft supply tube 302 and shaftreturn tube 304, respectively, within handle 180, using connecting means301 and 303. Connecting means 301 and 303 can be any means of connectingtwo tubes including but not limited to ultraviolet (UV) glue, epoxy orany other adhesive as well as friction or compression fitting. Arrows312 and 314 indicate the direction of flow of a cooling fluid suppliedby the one or more cooling devices 108, in such embodiments thatcomprise a cooling fluid as part of the cooling means. In this firstembodiment, shaft supply tube 302 and shaft return tube 304 arehypotubes made of a conductive material such as stainless steel. Thehypotubes extend from handle 180 through a lumen of hollow elongateshaft 184 to distal tip region 190, as shown in FIG. 4, wherein arrow408 indicates the direction of cooling fluid flow within a lumen 450defined by the one or more energy delivery devices 192. Thus, using theconfiguration described in a first embodiment of a system of theinvention, a cooling fluid is circulated between the one or more coolingdevices 108 and distal tip region 190 of at least one probe assembly106. As detailed later in the description, in alternate embodiments onehypotube may be used to supply cooling fluid to the one or more energydelivery devices 192 while two or more hypotubes may be used to returncooling fluid to the one or more cooling devices 108. The number ofhypotubes used for supplying cooling fluid and the number used forreturning cooling fluid and the combination thereof may vary and allsuch combinations are intended to be within the scope of the presentinvention.

In alternate embodiments of a system of the present invention, not allprobe assemblies may be cooled, in which case, the probe assemblies thatare not being cooled may not be associated with cooling tubes and theelongate hollow shafts of those probe assemblies may not comprise tubesfor supplying cooling to and returning cooling from the distal tipregions of those probe assemblies.

In this first embodiment of a system of the present invention, distalcooling supply tube 162 may be connected to distal cooling return tube164 in order to keep the tubing used in a system of the invention asorganized as possible. This connection may be temporary, such as with acable tie or other temporary connecting means, or may be more permanent,for example by using some form of adhesive bonding. Whether temporary ormore permanent, this connection can be achieved using various means ofconnecting two or more tubes and the present invention is not limited inthis regard. Referring again to FIG. 3, handle 180 may be at leastpartially filled with a filling agent 320 in order to lend more strengthand stability to handle 180 as well as to hold the various cables, tubesand wires in place. Filling agent 320 may be epoxy or any other suitablematerial. In addition, handle 180 is operable to easily and securelycouple to an optional introducer tube (discussed below) in a firstembodiment where an introducer tube would facilitate insertion of theone or more probe assemblies 106 into a patient's body. For example, asshown in FIG. 3, handle 180 may taper at its distal end in order toaccomplish this function, i.e. to enable it to securely couple to anoptional introducer tube.

In this first embodiment of a system of the present invention, hollowelongate shaft 184 is manufactured out of polyimide, which providesexceptional electrical insulation while maintaining sufficientflexibility and compactness. In alternate embodiments, hollow elongateshaft 184 may be any other material imparting similar qualities. Instill other embodiments, hollow elongate shaft 184 may be manufacturedfrom an electrically conductive material and may be covered by aninsulating material so that delivered energy remains concentrated atenergy delivery device 192 of distal tip region 190. In the firstembodiment, probe assembly 106 comprises a marker 384 at some pointalong handle 180 or along the length of elongate hollow shaft 184. In anembodiment where a probe assembly 106 is inserted into an optionalintroducer tube, marker 384 may be located on elongate hollow shaft 184(as shown in FIG. 3) and may be a visual depth marker that functions toindicate when the distal tip of the probe assembly is located at adistal end of the introducer tube by aligning with a hub of theintroducer tube. Marker 384 will thus provide a visual indication as tothe location of the distal tip of a probe assembly 106 relative to anoptional introducer tube. Alternatively, marker 384 may be a tactilemarker and may be used to indicate the orientation of a particularcomponent of probe assembly 106. For example, as discussed below, probeassembly 106 may comprise a secondary temperature sensor. In such anembodiment, marker 384 may serve to indicate the radial location of thesecondary temperature sensor within probe assembly 106.

Referring in detail to FIG. 4, a perspective cut-away view of a firstembodiment of distal tip region 190 of probe assembly 106 is shown. Inthis embodiment, distal tip region 190 comprises one or more temperaturesensing elements 402 which are operable to measure the temperature atand proximate to the one or more energy delivery devices 192. The one ormore temperature sensing elements 402 may comprise one or morethermocouples, thermometers, thermistors, optical fluorescent sensors orany other means of sensing temperature. In the first embodiment, the oneor more temperature sensing elements 402 are connected to generator 102via probe assembly cable 170 and cable 104 although any means ofcommunication between the one or more temperature sensing elements 402and generator 102, including wireless protocols, are included within thescope of the present invention. In the embodiment illustrated by FIG. 4,one or more temperature sensing elements 402 comprises a thermocouplejunction made by joining a stainless steel hypotube 406 to a constantanwire 410, wherein constantan wire 410 is insulated by wire insulation412. In this embodiment, the junction of hypotube 406 and constantanwire 410 is made by laser welding, although any other means of joiningtwo metals may be used. Furthermore, in this embodiment, hypotube 406and constantan wire 410 extend through a lumen of hollow elongate shaft184 and connect to probe assembly cable 170 within handle 180. In theembodiment shown in FIG. 4, the one or more temperature sensing elements402 protrudes beyond the one or more energy delivery devices 192. Inthis specific embodiment, whereby temperature sensing element 402comprises a stainless steel hypotube 406, stainless steel hypotube 406may be electrically conductive and may be electrically coupled to theone or more energy delivery devices 192. Thus, in such an embodimentwhereby energy may be conducted to the protrusion and delivered from theprotrusion to surrounding tissue, the protrusion may be understood to bea component of both temperature sensing element 402 as well as the oneor more energy delivery devices 192. Placing the one or more temperaturesensing elements 402 at this location, rather than within lumen 450defined by the one or more energy delivery devices 192, is beneficialbecause it allows the one or more temperature sensing elements 402 toprovide a more accurate indication of the temperature of tissueproximate to the one or more energy delivery devices 192. This is due tothe fact that, when extended beyond the one or more energy deliverydevices 192, the one or more temperature sensing elements 402 will notbe as affected by the cooling fluid flowing within a lumen 450 as itwould be were it located within lumen 450. Thus, in this embodiment ofthe present invention, probe assembly 106 comprises a protrusionprotruding from the distal region of the probe assembly, whereby theprotrusion is a component of temperature sensing element 402.

In the first embodiment of a probe assembly of the present invention,probe assembly 106 further comprises one or more secondary temperaturesensing elements 404 located within hollow elongate shaft 184 at somedistance away from one or more energy devices 192, and positionedadjacent a wall of hollow elongate shaft 184. For example, if the one ormore energy delivery devices 192 comprises an electrode that is 5-7 mmin length, then locating a secondary temperature sensing element 404approximately 3 mm away from a proximal end of said electrode is optimalfor measuring temperature at the periphery of an intervertebral disc asis discussed in more detail below. As mentioned above with respect tothe one or more temperature sensing elements 402, the one or moresecondary temperature sensing elements 404 may similarly comprise one ormore thermocouples, thermometers, thermistors, optical fluorescentsensors or any other means of sensing temperature. In the firstembodiment illustrated by FIG. 4, the secondary temperature sensingelement 404 is a thermocouple made by joining copper and constantanthermocouple wires, designated as 420 and 422 respectively. As mentionedearlier with respect to the one or more temperature sensing elements402, the copper and constantan wires 420 and 422 may extend through alumen of hollow elongate shaft 184 and may connect to probe assemblycable 170 within handle 180.

Probe assembly 106 may further comprise a thermal insulator 430 locatedproximate to any of the one or more temperature sensing elements 402 orthe one or more secondary temperature sensing elements 404. Thermalinsulator 430 may be made from any thermally insulating material, forexample silicone, and may be used to insulate any temperature sensingelement from other components of probe assembly 106, so that thetemperature sensing element will be able to more accurately measure thetemperature of the surrounding tissue. In the first embodimentillustrated by FIG. 4, thermal insulator 430 is used to insulate the oneor more secondary temperature sensing elements 404 from cooling fluidpassing through shaft supply tube 302 and shaft return tube 304.

As an additional feature of a first embodiment of a system of thepresent invention, probe assembly 106 comprises a radiopaque marker 440incorporated somewhere along hollow elongate shaft 184. For example, anoptimal location for a radiopaque marker may be at or proximate todistal tip region 190, adjacent the one or more energy delivery devices192 as shown in FIG. 4. Radiopaque markers are visible on fluoroscopicx-ray images and can be used as visual aids when attempting to placedevices accurately within a patient's body. These markers can be made ofmany different materials, as long as they possess sufficientradiopacity. Suitable materials include, but are not limited to silver,gold, platinum and other high-density metals as well as radiopaquepolymeric compounds. Various methods for incorporating radiopaquemarkers into or onto medical devices may be used, and the presentinvention is not limited in this regard.

In the first embodiment of a system of the present invention, radiopaquemarker 440 may comprise silver solder placed within hollow elongateshaft 184, proximate to the one or more energy delivery devices 192.When viewed under x-ray fluoroscopy, the silver solder will appear dark,allowing a user to readily distinguish the location of the solder. Ifthe solder is placed proximate to the one or more energy deliverydevices 192, then the one or more energy delivery devices 192 will bedistinguishable relative to other regions of hollow elongate shaft 184,allowing for accurate positioning of the one or more energy deliverydevices 192 at a treatment site within a body of a patient. Radiopaquemarkers 440 may also be incorporated by other methods, including but notlimited to vapor deposition, ion implantation, dip coating, metalplating and electro-plating. Further, there may be more than oneradiopaque marker 440 associated with probe assembly 106.

Cross-sectional views of portions of distal tip region 190, as indicatedin FIG. 4, are shown in FIGS. 5A and 5B. Referring first to FIG. 5A,three hypotubes 302, 304, and 406 are positioned within a lumen 450defined by hollow elongate shaft 184 and the one or more energy deliverydevices 192. Shaft supply tube 302 and shaft return tube 304 carrycooling fluid to and from the distal end of distal tip region 190,respectively. In this embodiment, hypotube 406 is made of a conductivematerial such as stainless steel and is operable to transmit energy fromprobe assembly cable 170 to the one or more energy delivery devices 192.In addition, hypotube 406 defines a lumen within which a means ofconnecting the one or more temperature sensing devices 402 to probeassembly cable 170 may be located. For example, if the one or moretemperature sensing devices 402 comprises a thermocouple, then aconstantan wire 410 may extend from probe assembly cable 170 to thethermocouple junction through hypotube 406 as is shown in FIG. 4.Alternatively, more than one wire may be passed through the lumen ofhypotube 406 or the lumen of hypotube 406 may be utilized for anotherpurpose.

In the first embodiment of the present invention, the one or more energydelivery devices 192 is an electrode, as discussed above. FIG. 5A is across-section of a portion of distal tip region 190 wherein hollowelongate shaft 184 and electrode 192 overlap in order to secure theelectrode in place. In this embodiment, the lumen defined by hollowelongate shaft 184 and electrode 192 at this portion of distal tipregion 190, contains a radiopaque marker 440 comprised of silver solder,as discussed above. The silver solder fills the lumen such that anycooling fluid supplied to probe assembly 106, that is not located withinone of the cooling tubes described earlier, is confined to the distaltip region 190 of probe assembly 106. Thus, in this embodiment, thesilver solder may be referred to as a flow impeding structure since itfunctions to restrict the circulation of fluid to a specific portion (inthis case, at least a portion of distal region 190) of probe assembly106. In other words, cooling fluid may flow from the one or more coolingdevices 108, through the cooling supply tubes described earlier, todistal tip region 190 of probe assembly 106. The cooling fluid may thencirculate within lumen 450 defined by electrode 192 in order to providecooling to the electrode. In the context of the present invention, aninternally-cooled probe is defined as a probe having such aconfiguration, whereby a cooling medium does not exit probe assembly 106from a distal region of probe assembly 106. The cooling fluid may notcirculate further down hollow elongate shaft 184 due to the presence ofthe silver solder, and flows through the cooling return tubes describedearlier back to the one or more cooling devices 108. In alternateembodiments, other materials may be used instead of silver solder, andthe invention is not limited in this regard.

Referring now to FIG. 5B, a cross-section of a portion of distal tipregion 190, proximal from the cross-section of FIG. 5A as illustrated inFIG. 4, is shown. In the embodiment illustrated by FIG. 5B, the one ormore secondary temperature sensing elements 404 is located proximate toan inner wall of hollow elongate shaft 184. This proximity allows theone or more secondary temperature sensing elements 404 to provide a moreaccurate indication of the temperature of surrounding tissue. In otherwords, the one or more secondary temperature sensing elements 404 may beoperable to measure the temperature of the inner wall of hollow elongateshaft 184 at the location of the one or more secondary temperaturesensing elements 404. This temperature is indicative of the temperatureof tissue located proximate to the outer wall of hollow elongate shaft184. Thus, it is beneficial to have the one or more secondarytemperature sensing elements 404 located proximate to an inner wall ofhollow elongate shaft 184, rather than further away from the inner wall.

As described above, thermal insulator 430 is placed between the one ormore secondary temperature sensing elements 404 and shaft supply andreturn tubes 302 and 304 in the first embodiment of the presentinvention. This serves to insulate the one or more secondary temperaturesensing elements 404 from the cooling effect of the cooling fluidlocated within shaft supply tube 302 and shaft return tube 304. Thus, byminimizing the cooling effect, one or more secondary temperature sensingelements 404 is able to provide a more accurate indication as to thesurrounding tissue temperature.

FIGS. 5A and 5B also illustrate the relative positions of the threehypotubes used in a first embodiment of a system of the presentinvention. In this embodiment, the three hypotubes are held together insome fashion in order to increase the strength of probe assembly 106.For example, the three hypotubes may be bound together temporarily ormay be more permanently connected using solder, welding or any suitableadhesive means. Various means of binding and connecting hypotubes arewell known in the art and the present invention is not intended to belimited in this regard.

As stated earlier, the figures included in this application, whichillustrate some embodiments of a system of the present invention, areintended to be exemplary only. For example, with respect to FIG. 5A, therelative positions of the three hypotubes as shown are not intended tolimit the scope of the invention in any way. It will be readily apparentto those skilled in the art that many variations are possible, relatingto both the number as well as the position of the hypotubes, all ofwhich are included within the scope of the present invention. Inalternate embodiments, the shape of the hypotubes may be optimized sothat more efficient use is made of a lumen defined by hollow elongateshaft 184 and the one or more energy delivery devices 192. In yetfurther embodiments, distal cooling supply tube 162 may provide coolingto the one or more energy delivery devices 192 without the use ofhypotubes, and this invention is intended to include any means ofsupplying cooling to and returning cooling from distal tip region 190,as well as any and all means of transmitting energy between probeassembly cable 170 and the one or more energy delivery devices 192. Forexample, one or more cooling devices 108 may comprise an electrothermalcooling device, as mentioned above. In such embodiments, the mechanismof supplying cooling to the one or more energy delivery devices 192 maydiffer significantly from the illustrated embodiment but is neverthelessincluded within the scope of the present invention.

As described above, providing cooling to probe assemblies 106 allowsheat delivered through energy delivery devices 192 to be translatedfurther into the tissue without raising the temperature of the tissueimmediately adjacent energy delivery device 192. FIGS. 6A-6C illustratevarious embodiments for the internal cooling of distal tip region 190 ofprobe assembly 106. Arrows 408, 630, and 660 indicate the direction offlow of the cooling liquid in FIGS. 6A, 6B, and 6C, respectively. FIG.6A shows a longitudinal cross-section of an internal liquid cooleddistal tip region 190 of the first embodiment of the present invention,as shown in FIG. 4. As described previously, the cooling supplymechanism comprises two hypotubes, shaft supply tube 302 and shaftreturn tube 304. In FIG. 6B, the cooling supply mechanism comprises asingle hypotube 600 defining a central bore 610 and an outer annularpassageway 620. Cooling liquid passes down the central bore 610, asindicated by arrow 630, and passes back through the outer annularpassageway 620.

FIG. 6C shows a cooling supply mechanism configured similarly to thatshown in FIG. 6B. However, in this embodiment, a single hypotube 640defines one or more apertures 650 proximate a distal tip region 190.Apertures 650 direct the flow of cooling liquid outward towards outerannular passageway 620. In this embodiment, hypotube 640 may be made ofa conductive material such as constantan and may be welded to energydelivery device 192 which may be made of a different conductive materialsuch as stainless steel. In this way, a junction between hypotube 640and energy delivery device 192 acts as a thermocouple useful to measuretemperature, in addition to providing channels for the flow of coolingliquid.

FIG. 7 shows a longitudinal cross-section of an embodiment of a distaltip region 190 further comprising an insulated impedance measuring tip700 adjacent the distal end of energy delivery device 192. Impedancemeasuring tip 700 can be used to help determine a position of energydelivery device 192 while the probe assembly 106 is being inserted intoa region of tissue. Impedance measuring tip 700 may be operable to sendvery small pulses of low power, high frequency current through thetissue to a dispersive ground electrode on the surface of the patient'sskin (not shown), or may be used in any other way of measuring impedanceknown in the art. Insulating material 710 isolates impedance measuringtip 700 from energy delivery device 192. As probe assembly 106 is movedthrough tissue, the impedance of the tissue can be measured, allowingthe location of energy delivery device 192 to be determined. Forexample, when impedance measuring tip 700 moves from the annulusfibrosis to the nucleus pulposus of an intervertebral disc, theimpedance level will drop. This drop in impedance effectively indicatesthat energy delivery device 192 is located within the annulus fibrosissince energy delivery device 192 is located proximally from impedancemeasuring tip 700 and is isolated from impedance measuring tip 700 byinsulating material 710. It will be understood to persons skilled in theart that the embodiments of the invention in which distal tip region 190comprises an impedance measuring tip will also include internal conduitsto hold wires that connect the impedance measuring tip to the generator102.

In some embodiments (not shown), distal tip region 190 may further beconfigured to predominantly expose one side of energy delivery device192, allowing increased control of the direction of energy delivery (notshown). This could be accomplished by incorporating an electricallyinsulating material into some regions of the energy delivery device, orthrough an associated insulation sleeve.

As mentioned above, system 100 of the present invention may furthercomprise one or more introducer tubes. Generally, introducer tubes maycomprise a proximal end, a distal end and a longitudinal bore extendingtherebetween. As previously stated with respect to a first embodiment ofthe present invention, introducer tubes (when used) are operable toeasily and securely couple with probe assembly 106. For example, theproximal end of the introducer tubes may be fitted with a connector ableto mate reversibly with handle 180 of probe assembly 106. An introducertube may be used to gain access to a treatment site within a patient'sbody and a hollow elongate shaft 184 of a probe assembly 106 may beintroduced to said treatment site through the longitudinal bore of saidintroducer tube. Introducer tubes may further comprise one or more depthmarkers in order to enable a user to determine the depth of the distalend of the introducer tube within a patient's body. Additionally,introducer tubes may comprise one or more radiopaque markers to ensurethe correct placement of the introducers when using fluoroscopicguidance.

In embodiments of the invention that include one or more introducertubes, the one or more introducer tubes may comprise one or moretemperature sensors along their lengths. In such embodiments, the one ormore temperature sensors may be placed proximate to the distal end ofthe one more introducer tubes so as to enable the one or moretemperature sensors to measure the temperature of tissue surrounding thedistal end of the one or more introducer tubes. For example, if a systemof the present invention, comprising introducer tubes, is used in atreatment procedure of an intervertebral disc, a temperature sensingelement located proximate to the distal end of the introducer tube maybe capable of monitoring the temperature of the periphery of theintervertebral disc, or of tissue surrounding the disc, when theintroducer tube is inserted into the disc. In other embodiments,multiple temperature sensing elements disposed along the introducer maybe used to indicate the size of the lesion as it expands. This may beparticularly useful in the treatment of tumor tissue, for example.

Introducer tubes may be made of various materials, as is known in theart and, if said material is electrically conductive, the introducertubes may be electrically insulated along all or part of their length,in order to prevent energy from being conducted to undesirable locationswithin a patient's body. In some embodiments, hollow elongate shaft 184may be electrically conductive, and an introducer may function toinsulate the shaft leaving the energy delivery device 192 exposed fortreatment. Further, the one or more introducer tubes may be operable toconnect to a power source and may therefore form part of an electricalcurrent impedance monitor (wherein at least a portion of the introducertube is not electrically insulated). Different tissues may havedifferent electrical impedance characteristics and it is thereforepossible to determine tissue type based on impedance measurements, ashas been described. Thus, it would be beneficial to have a means ofmeasuring impedance in order to determine the tissue within which adevice is located. In addition, the gauge of the introducer tubes mayvary depending on the procedure being performed and/or the tissue beingtreated. In one particular embodiment, the introducer tubes should besufficiently sized in the radial dimension so as to accept at least oneprobe assembly 106. In embodiments of a system of the present inventionlacking introducer tubes, hollow elongate shaft 184 may be insulated (inembodiments where hollow elongate shaft 184 is made of a conductivematerial) for the aforementioned reason, i.e. so as not to conductenergy to portions of a patient's body that are not being treated.Introducers may be manufactured from inconel or a similar non-magneticmetal to allow MRI- or CT-assisted placement.

In some embodiments of a system of the present invention comprising oneor more introducer tubes, the system may further comprise one or morestylets. A stylet may have a beveled tip to facilitate insertion of theone or more introducer tubes into a patient's body. Various forms ofstylets are well known in the art and the present invention is notlimited to include only one specific form. Further, as described abovewith respect to the introducer tubes, the one or more stylets may beoperable to connect to a power source and may therefore form part of anelectrical current impedance monitor. In other embodiments, one or moreprobe assemblies 106 may form part of an electrical current impedancemonitor, as has been mentioned with respect to FIG. 7. Thus, generator102 may receive impedance measurements from one or more of one or morestylets, one or more introducer tubes and one or more probe assemblies106 and may perform an action, such as alerting a user to an incorrectplacement of an energy delivery device 192, based on the impedancemeasurements.

In a first embodiment of a system of the present invention, first andsecond probe assemblies 106 are operated in a bipolar mode. In thisembodiment, electrical energy is delivered to first and second probeassemblies 106 and this energy is preferentially concentrated betweenfirst and second probe assemblies 106 through a region of tissue to betreated, as is discussed in greater detail below. The region of tissueto be treated is thus heated by the energy concentrated between firstand second probe assemblies 106. In other embodiments, first and secondprobe assemblies 106 may be operated in a monopolar mode, in which casean additional grounding pad would be required on the surface of a bodyof a patient, as is known in the art. Any combination of bipolar andmonopolar procedures may also be used.

In alternate embodiments, a system of the present invention may comprisemore than two probe assemblies. For example, in some embodiments, threeprobe assemblies may be used and the probe assemblies may be operated ina triphasic mode, whereby the phase of the current being supplieddiffers for each probe assembly.

As another feature of the present invention, a system may be configuredto control one or more of the flow of current between electricallyconductive components and the current density around a particularcomponent. For example, a system of the present invention may comprisethree electrically conductive components, including two of similar oridentical dimensions and a third of a larger dimension, sufficient toact as a dispersive electrode. Each of the electrically conductivecomponents should beneficially be operable to transmit energy between apatient's body and an energy source. Thus, two of the electricallyconductive components may be probe assemblies while the thirdelectrically conductive component may function as a grounding pad ordispersive/return electrode. In one embodiment, the dispersive electrodeand a first probe assembly are connected to a same electric pole while asecond probe assembly is connected to the opposite electric pole. Insuch a configuration, electrical current may flow between the two probeassemblies or between the second probe assembly and the dispersiveelectrode. In order to control the current to flow preferentially toeither the first probe assembly or the dispersive electrode, aresistance or impedance between one or more of these conductivecomponents (i.e. the first probe assembly and the dispersive electrode)and a current sink (e.g. circuit ‘ground’) may be varied. In otherwords, if it would be desirable to have current flow preferentiallybetween the second probe assembly and the dispersive electrode (as in amonopolar configuration), then the resistance or impedance between thefirst probe assembly and the circuit ‘ground’ may be increased so thatthe current will prefer to flow through the dispsersive electrode to‘ground’ rather than through the first probe assembly (since electricalcurrent preferentially follows a path of least resistance). This may beuseful in situations where it would be desirable to increase the currentdensity around the second probe assembly and/or decrease the currentdensity around the first probe assembly. Similarly, if it would bedesirable to have current flow preferentially between the second probeassembly and the first probe assembly (as in a bipolar configuration),then the resistance or impedance between the dispersive electrode and‘ground’ may be increased so that the current will prefer to flowthrough the first probe assembly to ‘ground’ rather than through thedispersive electrode. This would be desirable when a standard bipolarlesion should be formed. Alternatively, it may desirable to have acertain amount of current flow between the second probe assembly and thefirst probe assembly with the remainder of current flowing from thesecond probe assembly to the dispersive electrode (a quasi-bipolarconfiguration). This may be accomplished by varying the impedancebetween at least one of the first probe assembly and the dispersiveelectrode, and ‘ground’, so that more or less current will flow along adesired path. This would allow a user to achieve a specific, desiredcurrent density around a probe assembly. Thus, this feature of thepresent invention may allow a system to be alternated between monopolarconfigurations, bipolar configurations or quasi-bipolar configurationsduring the course of a treatment procedure.

As a further example of this feature of the present invention, fourelectrically conductive components may be provided. For example, asystem may comprise two probe assemblies as well as two dispersiveelectrodes and each electric pole may be connected to a single probeassembly and a single dispersive electrode. As was mentioned in theprevious example, the resistance or impedance between any of theelectrically conductive components and a current sink (e.g. circuit‘ground’) can be altered in order to control the flow of current betweencomponents. This configuration would be useful to selectively controlcurrent density around each probe assembly and thus selectively controltissue temperature and electrical field properties.

In yet another example of this feature, three substantially identicalelectrically conductive components, for example three probe assemblies,may be provided. In such a configuration, first and second probeassemblies may be connected to a single electric pole while a thirdprobe assembly may be connected to the opposite electrical pole. In suchan embodiment, the direction of current flow may be changed during thecourse of the procedure by varying the resistance or impedance betweeneach of the first and second probe assemblies and ‘ground’. Thus,current may flow in a bipolar fashion between the third probe assemblyand either the first or second probe assemblies, depending on whichprobe assembly provides a higher resistance or impedance to the currentflow. This system may be useful to alter the size or shape of atreatment area or lesion within a bodily tissue. Different energy modesas are known in the art may also be used depending on whether it isdesired to cut or coagulate the tissue.

As has been described, a system of the present invention optionallycomprises two or more temperature sensing elements, for example, oneassociated with the one or more energy delivery devices 192 and a secondassociated with one or more of hollow elongate shaft 184 or anintroducer tube. A secondary temperature sensing element may also belocated on a separate device inserted into the patient's body. FIG. 8illustrates an example of the utility of having two spaced-aparttemperature sensors. Two probe assemblies 106 are shown placed withinintroducer tubes 802, wherein distal tip regions 190 of probe assemblies106 are located within an intervertebral disc 800. Each of probeassemblies 106 comprises a hollow elongate shaft 184, an energy deliverydevice 192, a temperature sensing element 402 and a secondarytemperature sensing element 404. Temperature sensing element 402measures the tissue temperature at or proximate to energy deliverydevice 192 and, although temperature sensing element 402 is shown to beprotruding from the distal tip of energy delivery device 192, it will beclear to those skilled in the art that it may also be placed at otherlocations associated with energy delivery device 192 (for example,protruding from one side of energy delivery device 192). In thisembodiment, secondary temperature sensing element 404 is located withinhollow elongate shaft 184 or alternatively on the surface of hollowelongate shaft 184. In either case, secondary temperature sensingelement 404 is operable to measure the temperature of tissue at theperiphery of the disc as illustrated in FIG. 8. Thus, in addition tomeasuring the temperature at or proximate to energy delivery device 192,the temperature of tissue at the periphery of the disc is measured aswell. Measuring peripheral disc temperature may be beneficial in orderto ensure that tissue at the disc periphery or external to the disc isnot being overheated. FIG. 8 is intended to illustrate the utility ofhaving more than one temperature sensor and is intended to be exemplaryonly. The number and positions of the temperature sensors and thebenefits of having more than one temperature sensor are not limited tocooled probes and may differ depending on the application.

FIG. 9A illustrates an embodiment whereby a temperature sensor 900 islocated, via extrusion or another process, in a wall of hollow elongateshaft 184. By locating a temperature sensor at this position, thetemperature of the tissue surrounding the shaft can be measured as iswell understood by a person skilled in the art. Alternatively,temperature sensing elements may be located within probe assembly 106 soas to measure the temperature of inflow and outflow of cooling fluid. Bymeasuring the change in temperature of the inflow and outflow coolingfluid, the temperature of the tissue located adjacent energy deliverydevice 192 can be determined. In further embodiments, temperaturesensing elements may be positioned in any other location as needed. Forexample, in a treatment procedure involving an intervertebral disc,temperature sensors not associated with probe assemblies 106 may beplaced external to the disc, in the spinal canal, or in proximity to thespinal nerve.

FIG. 9B shows a distal tip region 190 of a probe assembly 106 with anextendible remote temperature sensing element 910 which may be deployedfrom probe assembly 106. The internal liquid cooling system has beenomitted for ease of illustration. Temperature sensing element 910 allowsmonitoring of the temperature within tissues located remotely from thesurface of energy delivery device 192. Temperature sensing element 910may be steerable so that its position may be changed during a procedureto obtain temperature measurements from a variety of tissue regions. Insuch an embodiment, the cooling feedback may be determined by acombination of temperatures within or surrounding the tissue beingtreated.

Any or all of the above embodiments of probe assembly 106 may comprisean active shape control mechanism to steer distal tip region 190, forexample as it is moved through the tissue. Such active shape controlmechanisms include, but are not limited to, cables for a mechanicalactuator, hydraulic or piezo-electric devices, and solenoids.

Usage of a first embodiment of a system 100 of the present invention totreat an intervertebral disc may be described generally as follows: Witha patient lying on a radiolucent table, fluoroscopic guidance is used topercutaneously insert an introducer with a stylet to access theposterior of an intervertebral disc. In addition to fluoroscopy, otheraids, including but not limited to impedance monitoring and tactilefeedback, may be used to assist a user to position the introducer orprobe assemblies within the patient's body. The use of impedancemonitoring has been described earlier, whereby a user may distinguishbetween tissues by monitoring impedance as a device is inserted into thepatient's body. With respect to tactile feedback, different tissues mayoffer different amounts of physical resistance to an insertional force.This allows a user to distinguish between different tissues by feelingthe force required to insert a device through a given tissue. One methodof accessing the disc is the extrapedicular approach in which theintroducer passes just lateral to the pedicle, but other approaches maybe used. A second introducer with stylet is then placed contralateral tothe first introducer in the same manner, and the stylets are removed.Probe assemblies 106 are inserted into each of the two introducersplacing electrodes 192 in the disc such that the distance betweenelectrodes 192 is 1 mm to 55 mm. Once in place, a stimulating electricalsignal may be emitted from either of electrodes 192 to a dispersiveelectrode or to the other electrode 192. This signal may be used tostimulate sensory nerves where replication of symptomatic pain wouldverify that the disc is pain-causing. A different signal may be used tostimulate motor nerves where a motor reaction indicates unsafe proximityto motor nerves that should not be heated. Probe assemblies 106 areconnected to an RF generator 102 as well as to peristaltic pumps 108 tocool distal tip regions 190. Radio frequency energy is delivered toelectrodes 192 and the power is altered according to the temperaturemeasured by temperature sensing element 402 in the tip of electrode 192such that a desired temperature is reached between the distal tipregions 190 of the two probe assemblies 106. During the course of theprocedure, a treatment protocol such as the cooling supplied to theprobe assemblies 106 and/or the power transmitted to the probeassemblies 106 may be adjusted in order to maintain a desirabletreatment area shape, size and uniformity. These adjustments may be madeon the basis of feedback from various sources, including but not limitedto temperature sensors and impedance sensors. In addition, the treatmentprotocols may be adjusted based on an error signal received by a controlmodule, which control module may be associated with generator 102. Thecooling devices may be independently controlled to alter the rate ofcooling to each electrode 192. Following treatment, energy delivery andcooling are stopped and probe assemblies 106 are removed fromintroducers. A fluid such as an antibiotic, an anesthetic or a contrastagent may be injected through the introducers, followed by removal ofthe introducers. Alternatively, the distal tips of the probe assemblies106 may be sharp and sufficiently strong to pierce tissue so thatintroducers may not be required. As mentioned above, positioning probeassemblies 106, and more specifically energy delivery devices 192,within the patient's body, may be assisted by various means, includingbut not limited to fluoroscopic imaging, impedance monitoring andtactile feedback. Additionally, some embodiments of this method aspectmay comprise one or more steps of inserting or removing material into apatient's body. For example, as has been described, a fluid may beinserted through an introducer tube during the course of a treatmentprocedure. Alternatively, a substance may be inserted through probeassembly 106, in embodiments where probe assembly 106 comprises anaperture in fluid communication with a patient's body. Furthermore,material may be removed from the patient's body during the course of thetreatment procedure. Such material may include, for example, damagedtissue, nuclear tissue and bodily fluids. Possible treatment effectsinclude, but are not limited to, coagulation of nerve structures(nociceptors or nerve fibers), ablation of collagen, biochemicalalteration, upregulation of heatshock proteins, alteration of enzymes,and alteration of nutrient supply.

A system of the present invention may be used in various medicalprocedures where usage of an energy delivery device may provebeneficial. Specifically, a system of the present invention isparticularly useful for procedures involving treatment of back pain,including but not limited to treatments of tumors, intervertebral discs,facet joint denervation, sacroiliac joint lesioning or intraosseous(within the bone) treatment procedures. Moreover, the system isparticularly useful to strengthen the annulus fibrosus, shrink annularfissures and impede them from progressing, cauterize granulation tissuein annular fissures, and denature pain-causing enzymes in nucleuspulposus tissue that has migrated to annular fissures. Additionally, thesystem may be operated to treat a herniated or internally disrupted discwith a minimally invasive technique that delivers sufficient energy tothe annulus fibrosus to breakdown or cause a change in function ofselective nerve structures in the intervertebral disc, modify collagenfibrils with predictable accuracy, treat endplates of a disc, andaccurately reduce the volume of intervertebral disc tissue. The systemis also useful to coagulate blood vessels and increase the production ofheat shock proteins.

As an illustration of the benefits of using a system of the presentinvention, some of the aforementioned procedures will now be describedin more detail. Although some of the figures and the description relateto the percutaneous insertion of the probes into an intervertebral discit will be understood that the probes can also be used during surgeryand can be inserted directly into a disc or other tissue through an opencavity.

Treatment of an intervertebral disc has already been mentioned briefly,but will now be described in more detail. FIG. 10 shows a lateral viewof a portion of a human spine with vertebrae 1000 and intervertebraldiscs 1010 showing the location of the nucleus pulposus 1020 in dashedoutline surrounded by overlapping layers of the annulus fibrosus. FIGS.11A and 11B are cross-sections through the intervertebral disc asindicated in FIG. 10. In the embodiment of the procedure shown in FIG.11A, energy delivery devices 192 of two probe assemblies 106 are locatedpartially in the nucleus pulposus and partially in the annulus fibrosisof intervertebral disc 1010 so that at least an equal amount of energyis delivered to the nucleus pulposus as to the annulus fibrosis. Analternate placement of probe assemblies 106 towards the anterior of theintervertebral disc is illustrated in FIG. 11B. Placement of probeassemblies 106 in this region of the disc could be used for treatinganterior fissures or for various other applications in the anteriorregion of the disc. Alternatively, for some procedures, one probeassembly 106 may be placed in the anterior and one in the posterior ofthe disc. Other placements are possible for probe assemblies 106depending on the desired treatment, and the invention is not intended tobe limiting in this regard.

Proper positioning of the probe assemblies 106 may be determined usingradiopaque markers associated with the introducer, stylet or probeassembly, or any combination thereof. Positioning may be furtherconfirmed by injecting a small amount of radiopaque contrast solutioninto the disc. The optimal distance between probe assemblies 106 mayvary according to disc location, disc size or geometry, hydration,degree of degeneration or other parameters. Motor and/or or sensorystimulation may be used before or after the procedure to confirm thelocation of the probe assemblies and the success of the procedure. Suchstimulation may be done in monopolar or bipolar modes, as described ingreater detail below.

Using a system of the present invention is beneficial because the use oftwo probe assemblies 106 in a bipolar configuration allows for thecreation of a relatively uniform lesion between the distal tip regions190 of the two probes. Using liquid-cooled probe assemblies 106 with anappropriate feedback control system as described above also contributesto the uniformity of the treatment. Cooling distal tip regions 190 ofprobe assemblies 106 helps to prevent excessively high temperatures inthese regions which may lead to tissue adhering to probe assemblies 106as well as an increase in the impedance of tissue surrounding distal tipregions 190 of probe assemblies 106. Thus, by cooling distal tip regions190 of probe assemblies 106, higher power can be delivered to tissuewith a minimal risk of tissue charring at or immediately surroundingdistal tip regions 190. Delivering higher power to energy deliverydevices 192 allows tissue further away from the energy delivery devices192 to reach a temperature high enough so as to create a lesion and thusthe lesion will not be limited to a region of tissue immediatelysurrounding energy delivery devices 192 but will rather extendpreferentially from an distal tip region 190 of one probe assembly 106to the other.

This concept is illustrated in FIG. 12A, showing a graph of temperaturevs. distance in a tissue with uniform thermal/electrical properties. Thedistal tip regions 190 of the two probe assemblies 106 are located atpositions p1 and p2 on the x-axis and the temperature needed to create alesion is noted as T_(LES) on the y-axis. In FIGS. 12A and 12B, solidlines 1202 and 1204 represent a cooled probe assembly, while dashedlines 1201 and 1203 represent a non-cooled probe assembly. In order tocreate a lesion extending from p1 to p2, a large amount of power must besupplied to energy delivery devices 192 so that the energy will betransmitted over a far enough distance away from energy delivery devices192 to create the lesion. Without the benefits of cooling, the higherthe power that is supplied to energy delivery device 192, the higher thetemperature around the energy delivery device 192 will be. Curve 1201shows a temperature profile, as may be typically achieved usingnon-cooled probes in a uniform tissue. In such a configuration it isdifficult to create a lesion extending from p1 to p2 because bysupplying a large amount of power to energy delivery device 192, thetemperature at the locations p1 and p2 of the distal tip regions reachesvery high levels. High temperatures at the distal tip regions may causenearby tissue to char and possibly adhere to distal tip regions 190.Furthermore, raising the temperature of tissue causes the impedance ofthe tissue to increase and limits the penetration of current into thetissue, thereby limiting the size of the lesion that can be created. Incontrast, cooled probe assemblies may be used to form a desired lesionbetween p1 and p2 while reducing such temperature effects. Curve 1202shows a typical temperature profile for a uniform tissue as may be seenwhen using two cooled probe assemblies. The temperatures at the distaltip regions, p1 and p2, are reduced relative to the surrounding tissuedue to the effect of the cooling. This allows for higher power to betransmitted to energy delivery devices 192 without concern for tissuecharring. In addition, because the temperature of tissue surroundingenergy delivery device 192 is reduced, the impedance of the surroundingtissue will not increase significantly and therefore current supplied byenergy delivery device 192 can penetrate more deeply into the tissue. Asillustrated in FIG. 12A, a lesion can therefore be created between p1and p2 using cooled probe assemblies 106 due to the lower localtemperatures at p1 and p2. Although FIG. 12A shows the temperature at p1and p2 to be below the lesioning temperature, the cooling supplied tothe cooled probe assemblies may be reduced or eliminated allowing thetemperature of tissue around p1 and p2 to increase in order to completethe lesion between p1 and p2.

In certain procedures, treatment with radio frequency energy in theabsence of tissue heating may be beneficial. For example, collagenproduction by chondrocytes has been shown to be increased by treatmentwith radio frequency energy. Alternatively, some other biochemical orbiological effect may be produced. FIG. 12B depicts energy vs. relativedistance in a similar graph to FIG. 12A, where curves 1203 and 1204depict non-cooled and cooled probe assemblies, respectively. Asdescribed above, the use of cooled probe assemblies allows the user todeliver more energy to larger tissue areas while minimizing the heatingeffects on tissue surrounding distal tip regions 190.

A system of the present invention may also be used in intraosseousprocedures. Such procedures can treat a tumor in the bone or todenervate a neural structure within the bone. In an intraosseousprocedure, introducer tubes are generally used to gain access to thebone to be treated, for example, a vertebra of a spinal column. In thecontext of this description, denervation refers to any function that isperformed on neural structures so as to intervene with the transmissionof a sensory signal (including pain signals) in a nerve associated withsaid neural structure. As is the case with procedures related tointervertebral discs, two probes may be inserted to spaced-apart siteswithin a bone and energy may be delivered to energy delivery meanslocated at the distal regions of the probes. One benefit of using twoprobe assemblies in a bipolar configuration, as in a system of thepresent invention, is that knowledge of the precise location of thetissue to be treated is not necessary. As has been mentioned, use ofbipolar probes allows for a lesion to be created preferentially betweenthe two energy delivery devices. Therefore, so long as the tissue to betreated (e.g. a tumor or a neural structure) is located substantiallybetween the distal regions of the two probes, it will generally beaffected by the treatment procedure. Further applications of a deviceand/or system of the present invention may include, but are limited to,the treatment of tumors in other parts of the body or for cardiacablation.

As an additional feature of the method aspect of the present invention,certain embodiments may further comprise a step of performing a functionto map the neural pathways in the tissue or to determine the proximityof one of the energy delivery devices 192 to a neural structure and thisstep may occur one or more times throughout the course of the procedure.This step can involve, in one embodiment, stimulation of the neuraltissue at one or more frequencies and subsequent observation todetermine the effect of said stimulation. For example, to assessproximity to the target nerve, electrical energy is applied to theenergy delivery device using a frequency that excites sensory nerves,typically 30-70 Hz with a current of up to 1 mA. To confirm that theprobe is not in proximity to an untargeted nerve, motor nervestimulation is performed typically at a frequency of 1-5 Hz and acurrent of 3-5 mA. As is well known in the art, various frequencies andvoltages can be used to stimulate both sensory and motor nerves.Observation of said stimulation can take the form of visual, sensory,mechanical, or electrical detection of muscle activity, or the form ofsensory or electrical detection of nociceptive or other sensory neuralactivity (e.g. temperature sensation). The electrical energy(“stimulation energy”) applied during this step is beneficially capableof eliciting a response from a neural structure without damaging theneural structure. Using this step, it can be determined whether a targetnerve or nerves has a function that would contraindicate its ablation orfunctional alteration. In one embodiment, the lack of a contraindicationwould lead to the step of delivering energy, whereas the presence of acontraindication would lead back to the step of inserting one or moreprobe assemblies, whereby the step of inserting a probe assemblyincludes modifying the position of a probe assembly within the body.Furthermore, in some embodiments, a method of this aspect of the presentinvention may comprise a step of stimulating neural tissue after atreatment procedure in order to determine the effectiveness of thetreatment procedure. A stimulation step, as has been described, may beperformed in a monopolar mode, wherein energy configured to stimulate anerve is concentrated around a distal tip region of a single probeassembly in order to asses the proximity of neural tissue to that probeassembly. Alternatively, a stimulation procedure may be performed in abipolar mode, wherein energy configured to stimulate a nerve ispreferentially concentrated between the distal tip regions of two probeassemblies, thus allowing a user to detect neural tissue locatedsubstantially between the probe assemblies. In general, it may bebeneficial to perform a stimulation step employing a similar probeassembly configuration as will be used to deliver energy. Thus, ifenergy will be delivered using a monopolar configuration, it may bebeneficial to perform a stimulation step in a monopolar configuration aswell. Similarly, if energy will be delivered using a bipolarconfiguration, it may be beneficial to perform a stimulation step in abipolar configuration, as has been described.

As has been mentioned, a system of the present invention may be used toproduce a relatively uniform lesion substantially between two probeassemblies 106 when operated in a bipolar mode. Oftentimes, uniformlesions may be contraindicated, such as in a case where a tissue to betreated is located closer to one energy delivery device 192 than to theother. In cases where a uniform lesion may be undesirable, using two ormore cooled probe assemblies 106 in combination with a suitable feedbackand control system may allow for the creation of lesions of varying sizeand shape. For example, preset temperature and/or power profiles thatthe procedure should follow may be programmed into a generator prior tocommencement of a treatment procedure. These profiles may defineparameters (these parameters would depend on certain tissue parameters,such as heat capacity, etc.) that should be used in order to create alesion of a specific size and shape. These parameters may include, butare not limited to, maximum allowable temperature, ramp rate (i.e. howquickly the temperature is raised) and the rate of cooling flow, foreach individual probe. Based on temperature or impedance measurementsperformed during the procedure, various parameters, such as power orcooling, may be modulated, in order to comply with the preset profiles,resulting in a lesion with the desired dimensions.

Similarly, it is to be understood that a uniform lesion can be created,using a system of the present invention, using many different pre-settemperature and/or power profiles which allow the thermal dose acrossthe tissue to be as uniform as possible, and that the present inventionis not limited in this regard.

It should be noted that the term radiopaque marker as used hereindenotes any addition or reduction of material that increases or reducesthe radiopacity of the device. Furthermore, the terms probe assembly,introducer, stylet etc. are not intended to be limiting and denote anymedical and surgical tools that can be used to perform similar functionsto those described. In addition, the invention is not limited to be usedin the clinical applications disclosed herein, and other medical andsurgical procedures wherein a device of the present invention would beuseful are included within the scope of the present invention.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

1. A method of treating spinal tissue of a patient's body, the methodcomprising: providing a system comprising an energy source and first andsecond internally-cooled probe assemblies, wherein each of the probeassemblies comprises an electrically conductive energy delivery deviceelectrically coupled to said energy source; inserting the energydelivery devices of said first and second internally-cooled probeassemblies into spaced-apart treatment sites for said spinal tissue; anddelivering energy from said energy source to said spinal tissue throughsaid energy delivery devices.
 2. The method of claim 1, wherein the stepof inserting said energy delivery devices further comprises a step ofinserting at least one introducer tube into a patient's body and whereinsaid energy delivery devices are inserted into the treatment sitesthrough a bore of said at least one introducer tube.
 3. The method ofclaim 1, wherein the step of inserting said energy delivery devicescomprises utilizing an aid to assist in positioning at least one of saidenergy delivery devices.
 4. The method of claim 3, wherein said aid isselected from the group consisting of fluoroscopic imaging, impedancemonitoring and tactile feedback.
 5. The method of claim 1, furthercomprising the steps of: providing an apparatus operable to deliver acooling means to one or more probe assemblies when said one or moreprobe assemblies is located at a treatment site in a patient's body; anddelivering said cooling means to at least one of said first and secondprobe assemblies while said energy delivery devices are located at saidspaced-apart treatment sites.
 6. The method of claim 1, furthercomprising a step of delivering stimulating energy through at least oneof said energy delivery devices for determining proximity of at leastone of said energy delivery devices to a neural structure, wherein saidstimulating energy is capable of eliciting a response from said neuralstructure without damaging said neural structure.
 7. The method of claim6, wherein said step of delivering stimulating energy comprisesdelivering said stimulating energy preferentially between said energydelivery devices in a bipolar manner.
 8. The method of claim 1, furthercomprising a step of at least one of inserting material to and removingmaterial from said spinal tissue, wherein said step of at least one ofinserting and removing material is performed at least one of before andafter the delivery of energy.
 9. The method of claim 8, wherein the stepof inserting material comprises injecting a treatment composition intosaid spinal tissue and wherein said treatment composition is selectedfrom the group consisting of an anesthetic, a dye and an antibiotic. 10.The method of claim 1, further comprising a step of providing at leastone additional electrically conductive component coupled to said energysource and operable to transmit energy between said energy source andsaid patient's body.
 11. The method of claim 10, further comprising astep of controlling a flow of energy between at least two electricallyconductive components selected from the group consisting of said firstprobe assembly, said second probe assembly and said at least oneadditional electrically conductive component.
 12. The method of claim11, wherein said step of controlling a flow of energy comprises alteringan electrical impedance between a current sink and at least oneelectrically conductive component selected from the group consisting ofsaid first probe assembly, said second probe assembly and said at leastone additional electrically conductive component.
 13. The method ofclaim 1, wherein said spinal tissue is selected from the groupconsisting of an intervertebral disc, spinal neural tissue and avertebra or portions thereof.
 14. The method of claim 1, wherein saidenergy source is an electrical generator and wherein the step ofdelivering energy comprises delivering electrical current in a radiofrequency range.
 15. The method of claim 1, wherein said energy deliverydevices are operated in a bipolar mode, whereby delivered energy ispreferentially concentrated between said energy delivery devices. 16.The method of claim 1, wherein said system further comprising acontroller operable to control at least one aspect of a treatmentprotocol selected from the group consisting of energy delivery andcooling supply and wherein said controller is operable to control saidat least one aspect based on at least one of a temperature measurement,an impedance measurement and an error signal.
 17. The method of claim16, further comprising a step of measuring a treatment parameterselected from the group consisting of temperature and impedance andaltering said at least one aspect of a treatment protocol based on ameasured treatment parameter.
 18. The method of claim 1, wherein saidinternally-cooled probe assemblies each comprising: an elongate memberhaving a distal region and a proximal region and defining a lumentherebetween; an energy delivery device associated with said distalregion of said elongate member, said energy delivery device comprising aprotrusion; and a temperature sensor associated with said protrusion.19. The method of claim 1, wherein said internally-cooled probeassemblies each comprising at least two tubular members disposed withinsaid lumen for delivering a cooling fluid to and removing a coolingfluid from said energy delivery devices.
 20. A method of treating spinaltissue of a patient's body by delivering energy from an energy source tosaid patient's body, the method comprising the steps of: providing firstand second internally-cooled probe assemblies and at least oneadditional electrically conductive component, wherein each of the probeassemblies comprises an electrically conductive energy delivery deviceelectrically coupled to said energy source; delivering energy from saidenergy source to spaced-apart treatment sites for said spinal tissuethrough said energy delivery devices; and altering an electricalimpedance between a current sink and at least one electricallyconductive component selected from the group consisting of said firstprobe assembly, said second probe assembly and said at least oneadditional electrically conductive component; whereby altering anelectrical impedance serves to adjust a flow of energy between at leasttwo electrically conductive components selected from the groupconsisting of said first probe assembly, said second probe assembly andsaid at least one additional electrically conductive component.